Cushion and mask therefor

ABSTRACT

A nasal cushion ( 30 ) comprises a substantially triangularly shaped frame ( 32 ) from which extends a membrane ( 34 ). The frame ( 32 ) has a scalloped edge ( 36 ) by which the cushion ( 30 ) is affixed to a mask body. The membrane ( 34 ) has an aperture ( 38 ) into which the wearer&#39;s nose is received. The membrane ( 34 ) is spaced away from the rim ( 40 ) of the frame ( 32 ), and its outer surface ( 41 ) is of substantially the same shape as the rim ( 40 ). Respective notches ( 42,44 ) receive the bridge of the wearer&#39;s nose. The wearer&#39;s nose is received through the aperture ( 38 ) into the chamber within the mask body ( 46 ). The seal forming portion ( 45 ) thus contacts both the surface of the wearer&#39;s nose and a portion of the wearer&#39;s face in the region between the base of the nose and the upper lip, and around the sides and over the bridge of the nose. The shape of the seal forming portion ( 45 ) is particularly suited to effectively seal the difficult region of the facial contour that is the crease between the sides of the nose and the face.

FIELD OF THE INVENTION

The invention relates generally to a nasal mask and to a cushiontherefor, for example, for use in the treatment of respiratoryconditions and in assisted respiration.

BACKGROUND OF THE INVENTION

Nasal masks are commonly used in the treatment of respiratory conditionsand sleep disorders (e.g., obstructive sleep apnea) by delivering a flowof breathable gas for, or to assist patient respiration. These nasalmasks typically receive a gas supply line which delivers gas into achamber formed by walls of the mask. The walls usually are semi-rigidand have a face contacting portion including an aperture which isaligned with the wearer's nostrils. The face contacting portion cancomprise a soft, resilient elastomeric material which may conform tovarious facial contours. The mask normally is secured to the wearer'shead by straps. The straps are adjusted to pull the mask against theface with sufficient force to achieve a gas tight seal between the maskand the wearer's face. Gas is thus delivered to the mask and through theaperture to the wearer's nasal passages.

Problems often arise with masks of the above configuration. For example,the mask may be dislodged, thereby breaking the seal between the maskand wearer. This may occur if the wearer rolls over when sleepingthereby creating a drag force on the gas supply line which istransmitted to the mask, breaking the seal. In the case of a mask beingused for the administration of Continuous Positive Airway Pressure(CPAP) treatment for the condition obstructive sleep apnea, such a leakcan result in the pressure supplied to the entrance of the wearer'sairway being below the therapeutic value, and the treatment becomingineffective.

Another problem is that the face contacting portion may apply excessivepressure to the wearer's face resulting in discomfort and possibly skinirritation. This can occur because the face contacting portion has todistort beyond its normal range of elasticity to conform to certainfacial contours which requires the application of excessive forces. Insome cases these excessive pressures and forces may cause the face todistort to conform with the face contacting portion to increase wearerdiscomfort, facial soreness and ulceration.

Other types of devices exist whereby small nostril nosepieces (pillows)are held in place by a harness strapped over the wearer's head, forexample as shown in prior art U.S. Pat. No. 4,782,832 (Trimble et al).While this arrangement may alleviate some problems regarding sealbreakage and skin abrasion, the harnesses associated with such devicesare quite cumbersome for the wearer, as are the gas supply lines. Also,air ‘jetting’ into the nostrils can be irritating to the patient makingsuch devices generally uncomfortable to use.

A further example of the prior art also is disclosed in U.S. Pat. No.5,243,971 (Sullivan et al).

Cushion masks have also been developed. These cushion masks have aninflated cushion which provides comfort to the wearer. However, thesemasks, under certain circumstances, may form a tuck or pucker resultingin a leak.

It is an object of the invention to overcome or at least substantiallyameliorate one or more of the foregoing disadvantages.

SUMMARY OF THE INVENTION

In one broad form, the invention discloses a nasal mask cushion tosealingly connect a mask to a wearer's face, the cushion comprising:

-   -   a substantially triangularly-shaped frame of resilient material        having a rim to surround wearer's nose;    -   a membrane also of resilient material, said membrane being        relatively more flexible than said frame, and being of the same        general shape as said rim and fixed to and extending away from        said frame so as to have an outer surface spaced from said rim,        a portion of said outer surface forming a face contacting seal;        and    -   a nose-receiving cavity bounded by said frame and said membrane;    -   and wherein said seal portion is generally coterminous with        respect to said rim and is resiliently deformable towards said        rim in use of said cushion.

In one particularly advantageous form, the membrane is substantiallysaddle-shaped. The membrane further has a centrally located aperturethrough which the wearer's nose passes to enter said cavity.

It is preferred that the cushion and membrane each include a co-locatednotch to accommodate the bridge of the nose of the wearer. Typically,the seal portion contacts at least the wearer's nose, and preferably,also the facial tissue around the sides and over the bridge of the noseand between the base of the nose and the top lip.

The invention further discloses a nasal mask for connection to awearer's face comprising:

-   -   a mask body for connection with a supply of breathable gas; and    -   a nasal cushion, the body and cushion defining a nose-receiving        cavity, said cushion including:    -   a substantially triangularly-shaped frame of resilient material        having a rim to surround said wearer's nose;    -   a membrane also of resilient material, said membrane being        relatively more flexible than said frame, and being of the same        general shape as said rim and fixed to and extending away from        said frame so as to have an outer surface spaced from said        frame, a portion of said outer surface forming a face contacting        seal;    -   and wherein said seal portion is generally coterminous with        respect to said rim and is resiliently deformable towards said        rim in use of said mask.

The mask body can further include attachment points from which securingstraps can be attached, and by which the mask can be secured to thewearer's head. The nasal mask can yet further comprise an arm dependingfrom said body from which a further securing strap(s) can be attached.

The invention further discloses nasal CPAP treatment apparatuscomprising a flow generator for the supply of gas at a pressure elevatedabove atmospheric pressure to a gas delivery conduit, the conduit inturn coupled to a nasal mask as described immediately above.

In one particularly preferred form, a supply of gas can be provided tosaid cavity, said supply of gas assisting, but not solely causingmaintenance of a seal by said seal forming portion of said membrane tothe face of the wearer in use of the cushion.

Advantageously, the membrane and the rim are substantially shaped to thefacial contour, and the membrane does not need to turn in on itself thuscontacting the face without folds or creases. With the cushion/masksecured to the wearer's head, the headstraps need only to be tensionedto balance the force due to mask gas pressure that tends to lift themask off the face. Such relatively lower mask-to-face pressure resultsin greater patient comfort, and a reduction in the likelihood of skinirritation.

BRIEF DESCRIPTION OF THE DRAWINGS

An embodiment of the invention will now be described with reference tothe accompanying drawings, in which:

FIG. 1 is a rear perspective view of a mask cushion embodying thepresent invention;

FIG. 2 is a cross-sectional view along line 1-1;

FIG. 3 is a perspective view of a nasal mask including the cushion ofFIGS. 1 and 2; and

FIG. 4 is a perspective view of the nasal mask of FIG. 5 secured to awearer's head.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 shows a perspective view of a nasal cushion 30 embodying theinvention. FIG. 2 shows the cross-sectional view along line 1-1. Thecushion 30 comprises a substantially triangularly shaped frame 32 fromwhich extends a membrane 34. The frame 32 has a scalloped edge 36 bywhich the cushion 30 is affixed to a mask body, as presently will bedescribed.

The membrane 34 has an aperture 38 into which the wearer's nose isreceived in use of the cushion 30. The membrane 34 is spaced away fromthe rim 40 of the frame 32, and its outer surface 41 is of substantiallythe same shape as the rim 40. The outer surface 41 of the membrane 34and the rim 40 of the frame 32 also can be described as generally saddleshaped. The shaping of the outer surface 41 of the membrane 34 and therim 40 of the frame 32 also include respective notches 42,44 thatreceive the bridge of the wearer's nose in use of the cushion 30.

As is best seen in FIG. 2, the frame 32 and the membrane 34 areintegrally formed, typically by in a one-shot molding process. The frame32 and the membrane 34 are fabricated from a resilient material. Onesuitable such material is Silastic™ silicone elastomer manufactured byDow Corning. The frame 32, in one preferred embodiment, has a typicalthickness at its rim 40 of 1.5 mm. The membrane 34, in a preferredembodiment, has a typical thickness of 0.35 mm. In this way, themembrane 34 is relatively more flexible than the rim 40.

In use of the cushion 30, a wearer's nose will be inserted in theaperture 38 to engage a seal forming portion 45 (formed between thedashed lines) of the outer surface 41 to cause deformation of themembrane 34. Depending upon the securing force supplied to the membrane34, it may deform to a point where it butts against the rim 40 of theframe 32. The frame 32 has a rigidity sufficient to withstand usualsecuring pressures in use of the cushion 30 to tend to retain its shapeand resist deformation. It thus acts as a supporting structure.

Referring now to FIG. 3, the nasal cushion 30 is shown attached to amask body 46 by the edge 36 of the frame 32, adhered or otherwisesecured to a flange 48 of the mask body 46. Only the outer surface 41 ofthe membrane 34 can be seen. The flange 48 includes three slots 50-54from which tensioning straps can be attached to secure the cushion 30and the mask body 46 (in combination) to the head of a wearer.

The mask body 46 forms a cavity that can receive the nose of the wearerby the aperture 38. A port 56 is provided at the top of the mask body 46by which breathable gas can be supplied to the chamber.

Referring now to FIG. 4, there is shown a nasal mask 60 including themask body 46 and the mask cushion 30. A coupling tube 62 is connected atone end with the inlet port 56, and at the other to a socket 64 intowhich can be received a gas delivery tube (not shown) for the supply ofbreathable gas to the chamber internal of the mask body 46. The maskbody 46 also has two vent openings 66 by which expired gas is exhausted.A first fastening strap 68 is fixed between to the lower two slots50,54. The upper slot 52 receives an arm 70, the top end of which has aresilient pad 72 to engage the forehead of the wearer. The arm 70 hastwo slots 74,76 along its side edges, by which a second fastening strap78 is secured.

In fitting the nasal mask 60, the wearer's nose is received through theaperture 38 into the chamber within the mask body 46. The seal formingportion 45 thus contacts both the surface of the wearer's nose and aportion of the wearer's face in the region between the base of the noseand the upper lip, and around the sides and over the bridge of the nose.The shape of the seal forming portion 45 is particularly suited toeffectively seal the difficult region of the facial contour that is thecrease between the sides of the nose and the face. Depending upon thetension applied by the fastening straps 68,78, a seal is formed with themembrane 34 remaining spaced from the rim 40 of the cushion frame 32.While the provision of pressurised gas to the chamber of the mask body46 assists in the maintenance of a seal between the membrane 34 and thewearer's nose and face, it is not essential in most cases, and aneffective seal will be formed absent any such pressurised gas. Onrelative movement of the mask 60 in relation to the wearer's head, thenose will be restrained by contacting the frame 32. Thus only limitedrelative motion between the mask 60 and the wearer's nose and faceoccurs.

The membrane 34 closely imitates the facial contour, and because of itsrelatively lesser stiffness than the frame 32, can conform to particularfacial structures with minimum force, and without a tendency to fold orcrease.

If the fastening strap 68,78 are tensioned to excess, the membrane 34deforms to abut the rim 40 of the cushion 32, the frame 32 thus actingas an “end limit”. In such a configuration, almost zero relativemovement can occur between the mask 60 and the wearer's head.

The nasal cushion 30 and nasal mask 60 has been described with referenceto CPAP or assisted respiration treatment, however it is to beunderstood that the invention generally is applicable to any applicationwhere gas and/or atomised liquid is to be supplied to the entrance ofthe nasal airways. Such applications include nebulisers, gas masks andanaesthetic machines.

1-23. Canceled.
 24. A mask cushion to sealingly connect a mask to awearer's face, the cushion comprising: a nasal bridge region, a cheekregion and a lower region below the cheek region; a substantiallytriangularly-shaped frame of resilient material having a first moldedinwardly curved rim; and a membrane of resilient material, said membranebeing thinner and more flexible than said first rim, said membranehaving a second molded inwardly curved rim, said second rim spaced adistance from said first rim, said distance grater than a thickness ofthe first rim, said distance measured when the mask is not in use, aportion of said second rim forming a face contacting seal.
 25. The maskcushion of claim 24, wherein the membrane is conformable, in use, tovarious facial structures with minimum force.
 26. The mask cushion ofclaim 25, wherein a maximum deformation position of the membrane isdefined by the rim.
 27. The mask cushion of claim 26, wherein themaximum deformation position is not reached under normal tighteningforce of the mask to the wearer's face.
 28. The mask cushion of claim24, wherein the frame, membrane and rim are formed as a one-piece unit.29. The mask cushion of claim 28, wherein the membrane has a thicknessof about 0.35 mm and the rim has a thickness of about 1.5 mm.
 30. A maskfor connection to a wearer's face comprising: a mask body for connectionwith a supply of breathable gas; and a cushion secured to said maskbody, the body and cushion forming a nose-receiving cavity, said cushionincluding: a nasal bridge region, a cheek region and a lower region; asubstantially triangularly-shaped frame of resilient material having amolded inwardly curved rim; and a membrane also of resilient material,said membrane being relatively more flexible than said rim, saidmembrane and rim being generally curved towards the nose-receivingcavity, said membrane arranged to generally cover the rim and beingspaced a distance from an outer surface of said rim at least in one ofthe bridge region, the cheek region or the lower region, said distancegreater than a thickness of the rim, said distance measured when themask is not in use, a portion of said membrane forming a face contactingseal; wherein said seal portion is resiliently deformable towards saidrim in use of said mask.
 31. The mask of claim 30, further comprising anarm coupled to and extending above the nasal bridge region of the mask,the arm including an oblong slot to receive a strap.
 32. The mask ofclaim 31, further comprising a single resilient pad mounted on the armand centered above the nasal bridge region of the mask.
 33. The mask ofclaim 30, wherein the membrane is conformable, in use, to various facialstructures with minimum force.
 34. The mask of claim 33, wherein amaximum deformation position of the membrane is defined by the rim. 35.The mask of claim 34, wherein the maximum deformation position is notreached under normal tightening force of the mask to the wearer's face.36. The mask of claim 30, wherein the frame, membrane and rim are formedas a one-piece unit.
 37. The mask of claim 30, wherein the rim is atleast twice as thick as the membrane.